Balyasny, based in Chicago and New York, opened an office in the U.K. capital in the past month and plans to have about 20 money managers at the location in 2014, up from three currently, Lancaster said. The firm also hired Adam Sutton, a money manager from London-based Eclectica Asset Management, who will be starting next month, Lancaster said.

Stamford-based SAC, run by Steven A. Cohen, said in October that it closed its London office, and in November agreed to pay $1.8 billion to settle charges by the U.S. government that it engaged in insider trading. SAC money managers in London have since been offered positions at hedge-fund firms including Louis Moore Bacon's Moore Capital Management and BlueCrest Capital Management.

SAC is transitioning to a family office and executives expect the firm will start 2014 with about $9 billion in assets, compared with $15 billion at the beginning of this year.